The present invention relates to electrographic recording. More particularly, it relates to an improved means and method for controlling the toner supply for such recording.
In the above-identified copending applicaton of Roger D. Erickson, there has been disclosed an electrographic recording system which includes means wherein toner powder having electrical and magnetic properties is carried from a hopper to a recording station by a rotatable drum or shell. The shell is rotated about a magnetic core structure which produces a magnetic field to hold the toner powder onto the surface of the shell as it rotates. At the recording station, a dynamic bridge of the toner powder is formed between the periphery of the drum or shell and a magnetically permeable member positioned a predetermined distance from the surface of the drum or shell. A record member is driven along a path between the drum and the permeable member with the reverse side of the record member in contact with the permeable member. An array of recording electrodes is positioned to be in electrical contact with the toner powder in the bridge. The record member is backed up by a platen member at least a portion of which is electrically conductive. When one or more of the electrodes is energized, a conductive path is established from the electrode, through the bridge, to the surface of the recording member and the conductive back-up platen, electrically charging the dielectric surface of a recording member to deposit toner powder thereon.
In the aforementioned copending application, the electrodes are positioned to be in electrical contact with the toner particles in the dynamic bridge. It has been found that the positioning of the magnetically permeable member relative to the magnetic core and the postioning of the electrodes or styli relative to the toner bridge is quite critical in order to produce optimum recording characteristics.